The Association of Interventricular Activation Delay With Clinical Outcomes in Cardiac Resynchronization Therapy

Published:November 23, 2022DOI:



      Pacing at sites of longest interventricular delay has been associated with greater reverse remodeling in cardiac resynchronization therapy (CRT). However, the effects of pacing at such sites on clinical outcomes is less well studied.


      To assess the association between interventricular delay and clinical outcomes in CRT patients implanted with quadripolar left ventricular (LV) leads.


      RALLY-X4 was a registry study of the Acuity X4 quadripolar LV leads. Interventricular delay was measured during unpaced basal rhythm from the right ventricular (RV) lead to the LV lead electrode (E1 to E4) chosen for CRT pacing. Patients were stratified by median RV-LV delay (80 ms) into short and long delay groups, and they were also analysed by multivariable modelling. The primary composite outcome measure was all-cause mortality and heart failure hospitalization (HFH) at 18 months.


      There were 581 patients with complete RV-LV delay data. The mean LV ejection fraction (EF) was 27% and 73% had a typical left bundle branch block. Predictors of long RV-LV delay included female sex, LBBB and QRS duration >150ms. Survival free of the primary outcome at 18 months follow up was 87% in the long activation delay group compared with 77% in the short delay group (p=0.0042). Multivariate analysis showed that RV-LV delay was a, independent predictor of survival free of HFH (p=0.028).


      Among CRT patients with quadripolar LV pacing leads, longer baseline interventricular activation delay was significantly associated with the composite endpoint of all-cause mortality and heart failure hospitalization.


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